Alternators are used to convert mechanical energy from a vehicle engine into electrical energy for the vehicle. The electrical energy produced by the alternator is used to charge the vehicle battery, and may also be used to power electric loads on the vehicle.
The alternator generally includes a rotatable field coil positioned on a rotor. The rotor is rotably positioned within a stator having a plurality of stator windings. Operation of the engine results in rotation of the rotor and the field coil. Current flowing through the rotating field coil results in a related current induced in the stator windings. Current flowing through the stator windings provides an output voltage that is rectified and delivered to the vehicle battery and/or electric loads on the vehicle.
Modern vehicle alternators include a regulator that controls the current through the field coil. When more current is provided to the field coil, the output of the alternator increases. When less current is provided to the field coil, the output of the alternator decreases.
Several different rotating electro-mechanical machine designs exist. One common design is the Lundell, or “claw-pole,” design. The claw-pole design is often used for dynamoelectric machines, such as alternators. In a claw-pole machine, the rotor includes claw-shaped pole segments (usually a pair of segments) located around one or more field windings. The pole segments have claw-shaped magnetic poles with poles on opposing segments interleaved in a meshing relationship.
Given the thermal conditions in which claw-pole machines often operate, proper cooling is vital to ensure proper and prolonged operation. Internal cooling fans are commonly used to cool claw-pole machines. Internal cooling fans are usually attached to the pole segments by welding or frictional clamping.
Conventional internal cooling fan attachment techniques are sometimes deficient in a variety of aspects. With conventional techniques, the choice of internal cooling fan material is restricted. For example, in order to weld a fan to a pole segment, the fan must be formed from a suitable material. It would therefore be advantageous to provide an attachment technique that expands the range of suitable materials used to form the fan.
Further, conventional attachment systems may be prone to fatigue and/or failure. Clamps and welds may degrade and eventually fail during prolonged operation. Moreover, when a fan is held to a segment through friction or welding, varnish from the field windings may wick in between the fan and the segment and be clamped upon in the assembly process. Because varnish has a low yield point in the typical alternator operating temperature range, it may yield to the pressure of the clamped assembly and the assembly may become loose. Thus, attachment methods providing increased durability over prolonged operation are also desired.